Materials Literature
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The vibrational properties of graphene fluoride and graphane are studied using ab initio calculations. We find that both sp3 bonded derivatives of graphene have different phonon dispersion relations and phonon densities of states as expected from the different masses associated with the attached atoms of fluorine and…
We demonstrate optical control of the LO phonon-plasmon coupled (LOPC) modes in GaAs by using a femtosecond pump-pulse pair. The relaxation time of the plasmon-like LOPC mode significantly depends on the separation time (Δt) of the pump-pulse pair. Especially it is maximized when Δt becomes simultaneously comparable t…
We propose an experimental technique to generate large amplitude coherent phonons with irradiation of THz-rate pump pulses and to study the dynamics of phase transition in GeTe ferroelectrics. When a single pump pulse irradiates the sample at various pump power densities, the frequency of the soft phonon decreases sub…
Sodium iridium(V) oxide, NaIrO3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO3, the much-studied structural analogue of the high-pressure post-perovskite phase of MgSiO3. Among the oxide post-perovskites, NaIrO3 is the first examp…
When a monolayer of hard microscale square platelets, produced lithographically, is osmotically concentrated in a flat plane to raise the particle area fraction Φ(A), an order-order transition occurs between a hexagonal rotator crystal and a rhombic crystal. Strikingly, phases having fourfold symmetry are not observed…
Using atomic force microscopy nanomanipulation, we position a single Au nanoparticle near a CdSe/ZnS quantum dot to construct a hybrid nanostructure with variable geometry. The coupling between the two particles is varied in a systematic and reversible manner. The photoluminescence lifetime and blinking of the same qu…
A novel graphene-on-organic film fabrication method that is compatible with a batch microfabrication process was developed and used for electromechanically driven microactuators. A very thin layer of graphene sheets was monolithically integrated and the unique material characteristics of graphene including negative th…
Formation energies of various intrinsic defects and defect complexes in ZnO have been calculated using a density-functional-theory-based pseudopotential all-electron method. The various defects considered are oxygen vacancy (${\mathrm{V}}_{\mathrm{O}}$), zinc vacancy (${\mathrm{V}}_{\mathrm{Zn}}$), oxygen at an inters…
Asymmetric polystyrene-polylactide (PS-PLA) bottlebrush block copolymers have been shown to self-assemble into a cylindrical morphology with large domain spacings. PLA cylinders can be selectively etched out of the shear-aligned polymer monoliths to generate nanoporous materials with an average cylindrical pore diamet…
Near-infrared (NIR) fluorescence sensing is desirable for in vivo biological measurements, but the method is currently limited by the availability of NIR fluorescent markers as well as by their poor performance, such as self-aggregation and dim fluorescence, in a physiological environment. To address this issue, this…
We report on the fabrication of electrically responsive nanoporous membrane based on polypyrrole doped with dodecylbenzenesulfonate anion (PPy/DBS) that was electropolymerized on the upper part of anodized aluminum oxide membrane. The membrane has regular pore size and very high pore density. Utilizing a large volume…
This paper presents research on the genetic structure and diversity of populations of a common marine protist and their changes over time. The bloom-forming diatom Skeletonema marinoi was used as a model organism. Strains were revived from anoxic discrete layers of a (210)Pb-dated sediment core accumulated over more t…
Birch reduction of few-layer graphene samples gives rise to hydrogenated samples containing up to 5 wt % of hydrogen. Spectroscopic studies reveal the presence of sp(3) C-H bonds in the hydrogenated graphenes. They, however, decompose readily on heating to 500 °C or on irradiation with UV or laser radiation releasing…
An analysis based on the energy conservation is presented for the self-propelled droplet during coalescence of two droplets of the same size over a superhydrophobic rough surface. The self-propelled behavior occurs only for the coalescence of droplets with a certain range of radius. An analytical relation is establish…
We present a robust method for forming high quality ohmic contacts to graphene, which improves the contact resistance by nearly 6000 times compared to untreated metal/graphene interfaces. The optimal specific contact resistance for treated Ti/Au contacts is found to average <10−7 Ω cm2. Additionally, we examine Al/Au,…
We report the development of a chitosan nanocarrier (NC)-based delivery of silver nanoparticles (Ag NPs) to mammalian cells for induction of apoptosis at very low concentrations of the NPs. The cytotoxic efficacy of the Ag NP-nanocarrier (Ag-CS NC) system in human colon cancer cells (HT 29) was examined by morphologic…
A ferroelectric-resistive random access memory consisting of a conductive BiFeO3 epitaxial thin film with a unipolar diode current modulated by electric polarization orientation is reported. This device has a memory that lasts for months, a sufficiently high on current and on/off ratio to permit ordinary sense amplifi…
A superaligned carbon nanotube (CNT) array is a special kind of vertically aligned CNT array with the capability of being converted into continuous fi lms and yarns. The as-produced CNT fi lms are transparent and highly conductive, with aligned CNTs parallel to the direction of drawing. After passing through volatile…
Subnanometer-sized copper nanoclusters were prepared by a one-pot procedure based on wet chemical reduction. The structural characteristics of the 2-mercapto-5-n-propylpyrimidine-protected nanoclusters, Cu(n) (n ≤ 8), were determined by mass spectrometry. The Cu nanoclusters displayed apparent luminescence, with dual…
We report direct mapping of the grains and grain boundaries (GBs) of large-area monolayer polycrystalline graphene sheets, at large (several micrometer) and single-atom length scales. Global grain and GB mapping is performed using electron diffraction in scanning transmission electron microscopy (STEM) or using dark-f…